For a fotodiode S2386 Hamamatsu TIW with photodiode parameters;
dark current 2pA
short current 6,5uA
Terminal capacitance 140pF
I would use the OPA3S328 with 5V single power supply. Is this a good choise? or what would you prefere?
If yes, is it possible to get the TINA circuite for OPA3S328?
Best regards
Joachim
HI Joachim,
The OPA3S328 is one option if you wish to build a transimpedance TIA amplifier with programmable gain. If I understood correctly, the maximum current for the Photodiode is 6.5nA. What is current range and resolution you need to resolve? Do you have any minimum TIA closed-loop circuit bandwidth requirements?
If you are require to use a +5V unipolar supply, we will need to bias the non-inverting terminal of the OPA3S328 to a voltage ~100mV above ground, so the OPA3S328 op-amp output has headroom above GND for output swing when there is no diode current, to keep the amplifier in the linear range. The photosensor will have a reverse voltage of ~100mV in the example below. Per the S2386 Hamamatsu datasheet, the dark current is small at 1pA typical with 100mV reverse biased. If you don't want to reverse bias the diode, we could power the op-amps with bipolar supplies, for example (V-)= -0.5V and (V+)=+5V.
The OPA3s328 input bias current is ±0.2pA typ, and the leakage current of the switches is in the ~10 picoamps at room temperature. Let me know if this is acceptable.
Below is just a quick preliminary TINA example with TIA gain RF2=698kΩ and RF1= 6.98MΩ but we can adjust gain per your current range requirement.
The simulations use the op-amp OPAx328 amplifier core model (same amplifier as OPA3S328), but use a simplified switch impedance model, but provide an accurate estimate of stability, noise, stability and bandwidth. See TINA-TI file below:
6888.OPA3S328_example_8-31-23.TSC
There is also a OPA3S328 application note that you may find useful:
Build a Programmable Gain Transimpedance Amplifier Using the OPA3S328
Thank you and Regards,
Luis
